Method and apparatus for sensing noise signals in a wireline communications environment

ABSTRACT

The present invention relates to methods and apparatuses for sensing noise sources in a wireline communications environment such as a customer premises environment in a DSL system. In embodiments, the invention includes an additional sensor that is connected to power mains in a DSL customer premises environment either to characterize, at their source, noises coupling into the DSL lines, and/or to mitigate their impact into the DSL lines. One objective is associated with diagnostics that help to better characterize the noise signals themselves and derive correlation of signals sensed from the power mains and their possible projection onto the DSL line. Another objective makes use of these power line sensor signals to mitigate or to eliminate power line noises that make their way onto the DSL line. Example embodiments further include and exploit signals from additional secondary sensors such as secondary common mode, differential mode and phantom mode sensors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/056,767 filed Oct. 17, 2013, which claims priority under 35 USC119(e) to prior co-pending U.S. Provisional Patent Application No.61/715,198, filed Oct. 17, 2012, the disclosures of which are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to wireline communications, andmore particularly to a sensor coupled to power lines for use incharacterizing and/or mitigating noise sources in a DSL modem.

BACKGROUND OF THE INVENTION

In a DSL deployment, stationary and impulsive noises are generatedwithin the home environment, which impact the reliability of the WANinterface of a residential device delivering network services such asIPTV. Sources of such disturbances include house appliances such asvacuum cleaners, lamps, or equipment such as pool pumps, washingmachines, etc. Apart from Differential Mode (DM) self-FEXT signals thatare expected to result primarily from a DM to DM coupling, in a houseenvironment DSL noise sources are assumed to originate predominantlyfrom a capacitive coupling due to the proximity in the house of thetwisted pair and the power supply mains on which are generated most ofthe domestic noise sources.

Some noise sources may be radiating externally directly into the twistedpair, which acts like an antenna to incoming waves. Such is the case forRFI disturbers that develop a common mode (CM) signal onto the drop andwhich get converted into a DM signal, without being necessarily presenton the power mains. But it is expected that most of the domestic noisesources find their way to the DSL line due to capacitive couplingbetween the mains network and the twisted pair, rather than throughradiation.

Relatedly, in traditional electromagnetic compatibility (EMC) compliancetesting of DSL modems illustrated in FIGS. 1 and 2, injection ofelectrical fast transients (EFTs) into the equipment under test (EUT)102 is performed in order to evaluate the immunity of modems againstinterferences that are representative of field conditions. Bursts ofEFTs are typically caused by operation of electro-mechanical switches,motors and distribution switch-gears connected to the power distributionnetwork. A typical burst consists of a large number of recurringimpulses at high frequency for a short time period. Since the EFTs areinherently travelling on the power distribution network within a house,these transients can make their way to the DSL port with which theyinterfere through at least two possible paths: first through acapacitive or inductive coupling of the power supply lines in the housewith the DSL cable itself, with which they come in close proximity; andsecondly, through leakage of the EFT signals through the power supplyleads to which the DSL modem is connected in order to receive its power.As a result of the multiplicity of possible coupling paths, immunitytests against EFTs are traditionally performed on the Telecom port (TP)and/or on the Power supply port. FIG. 1 illustrates the direct couplingof EFT signals into the DSL line itself by use of a coupling clamp 104.FIG. 2 illustrates the coupling of EFT signals through the power supplyport 106 of the DSL modem.

The principle by which the EFT signal impacts the DM DSL signal isillustrated as follows. FIG. 3 illustrates the EFT signal conversionthrough the loop imbalance following a capacitive coupling of the EFTsignal from the in-house mains network 302 and the DSL twisted pair 304.As the EFT signal travels on the power mains in-house network, a voltageV_(EFT) is developing on the hot/neutral pair of the in-house networkwith respect to a reference ground. At one specific or more couplingpoints within the house due to the proximity of the in-house power mainsnetwork 302 and the DSL twisted pair 304, this V_(EFT) signal couplesinto the DSL line and projects itself as a CM signal on the Tip and Ring(T&R) pair 308 of the DSL twisted pair, as a voltage V_(EFT-CM). The CMsignal on the twisted pair is then converted to a DM voltage V_(EFT-DM)due to the imbalance of the twisted pair with respect to ground. ThisV_(EFT-DM) signal superimposes itself onto the useful DSL signal andperturbs it. This scenario is captured in the test procedure shown inFIG. 1.

FIG. 4 illustrates the principle by which the EFT signal travelling ontothe in-house mains network 404 can leak through the power supply unit402 of the DSL modem, and converts itself into a DM signal at the T&R ofthe DSL modem port. As represented, the voltage V_(EFT) is developing onthe hot/neutral pair of the in-house network 404 with respect to areference ground. It is present on the power supply leads 406 thatprovide power to the DSL modem. Even if the power supply unit provides ahigh level of isolation for this unwanted signal, a certain voltageV_(EFT-CM) can make its way through leakage to the DSL front end, whichis electrically floating with respect to ground, thereby inducing a CMsignal present on the T&R pair 408 of the DSL twisted pair at the modem.This CM signal V_(EFT-CM) on the twisted pair is then converted to a DMvoltage V_(EFT-DM) due to the imbalance of the twisted pair with respectto ground, as seen at the point of injection. This V_(EFT-DM) signalsuperimposes itself onto the useful DSL signal and perturbs it. Thisscenario is captured in the test procedure of FIG. 2.

In actual field scenarios, however, the injection of the EFT signalstakes place simultaneously through capacitive coupling and power supplyleakage, since the EFT signals are expected to impact both interfaces ofthe modem simultaneously. This situation just illustrates the fact thatany modem (i.e. DSL link) may be susceptible to environmentalinterference on any of its physical interfaces (e.g. TP port, PowerSupply port, Ethernet port, Serial port, etc.) In this event, whenevertwo coupling paths exist together between the power mains and the DSLloop, either through the capacitive coupling of the loop (FIG. 3) orthrough the leakage of the power supply (FIG. 4), the resulting DM noiseon the DSL pair is actually a superposition of two separate noises whichcouple to the CM mode on the twisted pair, and then to DM throughdifferent transfer functions. FIGS. 3 and 4 illustrate that the CM to DMconversion of the signals that take place on the loop will be determinedby two different mode conversion transfer functions, which will bedifferent in the two cases due to the exact point of injection of the CMsignal resulting from the coupling of the power mains noise. At thesetwo points, which will be physically two distinct points on the cable(e.g. one point somewhere far from the modem (FIG. 3) and one pointclose to the modem (FIG. 4)), the imbalance of the cable that drives theconversion of the CM noise to DM as perceived by the modem is likely tobe different.

Accordingly, as illustrated in FIG. 5, there will be in effect twocoupling paths of interest: a signal conversion path 502 throughcapacitive/inductive coupling of the power mains into CM of T&R, whichthen gets converted to DM at a point of imbalance of the TP; and noisesignal conversion 504 from the power mains through the power supplyblock into T&R, that may get converted from CM to DM locally due to T&Rimbalance.

Those two paths of interest superimpose. Provided that the noise sourcesignals, which couple into the two points of imbalance, are identical,the resultant noise will appear to have coupled through a singleaggregate conversion path, due to the principle of superposition.

In practice, the coupling path through the power supply unit is undercontrol of the board designer. It should be minimized and reduced to alevel that is well below the coupling path that may exist between thepower mains network and the DSL line along the in-house network. In thisdiscussion, the manifestation of the noise leakage through the powersupply unit serves the purpose of illustrating the point developedhereafter that a connection path exists to the power mains noise throughthe power supply. The present inventors recognize that if controlled,this connection can be put to use efficiently for noise sourcecharacterization and mitigation into the DSL line.

The situation of coupling of noise through the power supply is notlimited to EFT noise sources; it was also observed by the presentinventors in a controlled lab environment with an HP-AV disturberconnected to the same power line as the modem. The leaked HP-AV signalcreated a measurable CM signal at the T&R, even though the T&R port ofthe modem was not connected to the cable. Whenever the modem wasconnected to the cable, the CM signal then got converted into a DMsignal on the T&R through the loop imbalance. This situation is anillustration that in practice, noise sources that are effectivelypresent on the power supply mains may find their way into the DSL portthrough power supply leakage.

In any event, in view of the foregoing, it would be desirable to be ableto characterize the CM noise generated by the power mains that couplesinto the DM DSL signal at its source.

SUMMARY OF THE INVENTION

The present invention relates to methods and apparatuses for sensingnoise sources in a wireline communications environment such as acustomer premises environment in a DSL system. In embodiments, theinvention includes an additional sensor that is connected to power mainsin a DSL customer premises environment either to characterize, at theirsource, noises coupling into the DSL lines, and/or to mitigate theirimpact into the DSL lines. One objective is associated with diagnosticsthat help to better characterize the noise signals themselves and derivecorrelation of signals sensed from the power mains and their possibleprojection onto the DSL line. Another objective makes use of these powerline sensor signals to mitigate or to eliminate power line noises thatmake their way onto the DSL line. Example embodiments further includeand exploit signals from additional secondary sensors such as secondarycommon mode, differential mode and phantom mode sensors.

In accordance with these and other aspects, an apparatus in a customerpremises environment of a wireline communication system according toembodiments of the invention includes a primary sensor coupled toreceive data signals of the wireline communication system; and a powerline sensor coupled to receive power line signals corresponding to noisesource interferences originating from power mains in the customerpremises environment.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention willbecome apparent to those ordinarily skilled in the art upon review ofthe following description of specific embodiments of the invention inconjunction with the accompanying figures, wherein:

FIG. 1 is a diagram that illustrates EFT injection on telecom port,representing a coupling between the in-house power line and the DSLline;

FIG. 2 is a diagram that illustrates EFT injection on power supply port,representing a coupling path through the power supply cable onto the DSLline;

FIG. 3 illustrates signal conversion through loop imbalance aftercapacitive coupling of in house mains network and twisted pair;

FIG. 4 illustrates signal conversion through loop imbalance afterleakage of in house mains network noise through the power supply unit(PSU);

FIG. 5 illustrates superposition of coupling paths;

FIG. 6 illustrates a Legacy Common Mode Sensor used in a dual sensorreceiver;

FIG. 7 illustrates an example Power Line Sensor in a Dual SensorReceiver according to embodiments of the invention;

FIG. 8 illustrates one example implementation of Power Line sensoraccording to the invention;

FIG. 9 illustrates another example of a power line sensor including Dualsensors using Hot & Neutral and Neutral & Ground connections accordingto the invention;

FIG. 10 illustrates another example of a power line sensor includingdual “DM and CM” sensors according to the invention;

FIG. 11 illustrates degeneracy of coupling paths due to differentweighted aggregate noises X and Y ;

FIG. 12 further illustrates degeneracy of coupling paths due todifferent weighted aggregate noises X and Y;

FIG. 13 illustrates concurrent use of a power line sensor(s) with asecondary DM sensor(s) on an unused pair according to embodiments of theinvention;

FIG. 14 illustrates an example of concurrent use of a power linesensor(s) with a secondary DM and PM sensors using an unused pairaccording to embodiments of the invention;

FIGS. 15 a and 15 b are graphs illustrating various modes of powerlinenoise in an example CPE environment;

FIGS. 16 a and 16 b are graphs illustrating various projections ofpowerline noise in an example CPE environment;

FIG. 17 a is a block diagram illustrating an example architecture formeasuring PSD, calculating correlation and cancelling variousprojections of noise according to embodiments of the invention;

FIG. 17 b is a graph illustrating an example PSD at the output ofcancellers shown in FIG. 17 a after recombination with a DM signal;

FIG. 18 is a block diagram illustrating an example multiple sensorreceiver for performing correlation and cancellation according toembodiments of the invention;

FIG. 19 is a block diagram illustrating an example noise monitor andnoise finder module using the multiple sensor signals of the presentinvention; and

FIG. 20 is a flowchart illustrating an example noise analysis processfor use in the module illustrated in FIG. 19 according to embodiments ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference tothe drawings, which are provided as illustrative examples of theinvention so as to enable those skilled in the art to practice theinvention. Notably, the figures and examples below are not meant tolimit the scope of the present invention to a single embodiment, butother embodiments are possible by way of interchange of some or all ofthe described or illustrated elements. Moreover, where certain elementsof the present invention can be partially or fully implemented usingknown components, only those portions of such known components that arenecessary for an understanding of the present invention will bedescribed, and detailed descriptions of other portions of such knowncomponents will be omitted so as not to obscure the invention.Embodiments described as being implemented in software should not belimited thereto, but can include embodiments implemented in hardware, orcombinations of software and hardware, and vice-versa, as will beapparent to those skilled in the art, unless otherwise specified herein.In the present specification, an embodiment showing a singular componentshould not be considered limiting; rather, the invention is intended toencompass other embodiments including a plurality of the same component,and vice-versa, unless explicitly stated otherwise herein. Moreover,applicants do not intend for any term in the specification or claims tobe ascribed an uncommon or special meaning unless explicitly set forthas such. Further, the present invention encompasses present and futureknown equivalents to the known components referred to herein by way ofillustration.

Among other things, the present inventors recognize that in the eventthat the home power mains is the main concentration point where themajority of domestic noise sources propagate in a house, before they getcoupled through a capacitive or inductive coupling to the twisted pairCM or DM modes, a sensor coupled directly to the home power mains (e.g.through a modem power supply port) would allow the collection of thenoise at its source. Such a sensor can be complementary or analternative to a CM noise sensor applied at the T&R pair, which has beentraditionally considered for use to cancel the converted CM noise ontothe DM signal.

FIG. 15 a illustrates the signals present in a typical houseenvironment. Across 17 MHz (VDSL bandwidth of interest), three PSDs ofsignals are displayed. A CM signal PSD 1502 on the twisted pair, a DMsignal PSD 1504 on the twisted pair and a powerline Hot Neutral signalPSD 1506 with 30 dB attenuation on a power outlet onto which the CPEmodem is connected. All three curves show peaks 1508 located at the samefrequencies, thereby illustrating the high level of correlation of thethree noise signals DM, CM and PL. FIG. 15 b provides a time domain viewof the frequency domain samples collected over a window of 5.5 MHz to7.7 MHz, for the DM signal 1510, CM signal 1512 and PL signal 1514.There again a similar time domain structure of the noise is detectableon all three signals, further justifying the benefits of looking atthese signals in search of correlation.

FIG. 16 a illustrates the normalized correlation results of two of thesignals at a time over the first 8 MHz bandwidth. Curve 1602 consists inthe correlation of CM and PL samples. Curve 1604 corresponds tocorrelation of CM and DM samples, while curve 1606 corresponds to thecorrelation of DM and PL samples. It is worth noticing that the CM-PLcorrelation 1602 is the highest, while the DM-PL correlation 1606 is thelowest. FIG. 16 b further gives insight into these results, by comparingthe correlation results of DM and PL samples to the results obtained bymultiplying the correlation results of CM to DM by the correlationresults of PL to CM. The relative matching of the two sets of curvesderived as explained earlier comports with the observation that a powerline noise signal will couple to a differential mode signal on thetwisted pair in a two-step process, which consists of a conversion of PLnoise into a CM noise on the twisted pair and then a conversion of theCM noise into a DM noise on the twisted pair.

FIG. 17 a illustrates from which input signals the various quantities ofPSD 1706 and correlation 1708 derived in connection with FIGS. 15 and 16are obtained. FIG. 17 a also illustrates the presence of two cancellersK_(DM-CM) 1702 and K_(DM-PL) 1704 that operate respectively on DM and CMinputs Yd and Yc, and on DM and PL inputs Yd and Ypl in order to yieldfrom adders 1714 each an output Yd′ and Yd″, in which correlated noisefrom the CM sensor and of the PL sensor have been removed respectivelyby cancellers K_(DM-CM) and K_(DM-PL). FIG. 17 b illustrates the PSD atthe output of those cancellers after recombination with the DM signal.One can appreciate that with each canceller the noise PSD output isreduced with respect to the PSD of the DM mode signal, therebyillustrating the process by which DM correlated noise with each of thesensor CM and PL has been removed. It is worth noting that the PSD withthe Dual Sensor Reference input as CM (curve 1710) is generally lowerthan the PSD with the Dual Sensor Reference input as PL (curve 1712).These results concur with the observation that less correlation isobserved between the PL sensor and the DM sensor, as compared to thecorrelation observed between the CM sensor and the DM sensor. In bothscenarios, noticeable improvement is observed with any of the twosensors for the purpose of mitigating correlated noise in the DM line,thereby justifying the value of using a PL sensor as a substitute orcomplimentary sensor to a CM sensor for the purpose of mitigatingexternal noise that impacts the DSL line.

As described below, embodiments of the invention generate a sensorsignal from an AC power supply wall wart that typically includes a twoor three prong plug on one end for connecting to a wall outlet of apower mains and a jack on the other end for connecting to a DC powersupply port of a DSL modem. The extra sensor can be used as analternative to, or jointly with other secondary sensors, such as acommon mode sensor. The combination of the power sensor output with theprimary sensor of the DSL line can be performed in the frequency domainand/or time domain, with various possible alternatives. An advantage ofthe invention lies in the sensing of AC power noises on the medium wherethey originate—the in-house power mains network, as they couple to theDSL line used in the house.

According to additional aspects, the present inventors also recognizesome limitations with the use of a sensor coupled to a DC power supplyoutput. For example, the DC power supply is designed to filter unwantedAC noise. A significantly attenuated noise should consequentially onlybe measurable. However, observations with HP-AV noise suggest that sincea non-insignificant signal level is measured on the DSL port withoutbeing connected externally to a cable, there should be some usablesignal level at the DC power supply output. The signals from the powersupply sensor may not only contain AC noise of interest from the mains,but it may also contain noises generated by devices on the board withinthe modem. Proper isolation of the sensor to these unwanted board noisesis therefore required.

FIG. 6 depicts a legacy common mode sensor used in a dual sensor DSLtransceiver. Conventionally, a CM noise sensor is applied at the T&Rpair, and the signal thereof has been traditionally considered for useto cancel the converted CM noise onto the DM port. As shown in FIG. 6,the primary connection of the AFE and Line Driver 602 is the DMconnection to the T&R pair to sense the differential DSL signal. Anadditional sensor 606 connects between the midpoint of the T&Rtransformer 608 and a reference point to sense a replica of the CMsignal that is present on the T&R with respect to a reference ground.FIG. 6 further depicts the modem power supply unit 610, as it existstoday and which generates DC reference voltages 612 for the modemoperation. In this configuration, the dual sensor receiver consists of atraditional DM sensor 602 and a CM sensor 606, which can be used jointlyeither to characterize the unwanted CM noise sources which convert fromCM to DM (Characterization), or to mitigate the impact of the CM noiseconversion into the DM DSL signal (cancellation).

FIG. 7 depicts a power line sensor used in embodiments of a DSLtransceiver according to certain aspects of the invention. As shown inFIG. 7, the primary connection of the AFE and Line Driver 702 is stillthe differential mode connection to T&R 704 to sense the DM DSL signal.An additional sensor 706 connects through a transformer 708 to one ofVoltage points derived from the Power Supply mains and a reference pointV_TBD via input 714, in order to sense a replica of the noise signalthat is present on the power supply mains. FIG. 7 further depicts themodem power supply unit 710, which generates the various DC referencevoltages 712 for the modem operation, which can be one of the points towhich the alternative sensor 706 can be connected. In this exampleconfiguration, the dual sensor receiver consists of a traditional DMsensor 702 and a power line sensor 706, which can be used jointly eitherto characterize the unwanted power mains noise sources which couple toCM on the twisted pair and then to convert to DM (Characterization), orto mitigate the impact of noise sources originating from the power mainsand which get converted into DM, thereby affecting DSL signals(cancellation).

Various implementations of input 714 that couple a power line sensor 706to voltage points in the power supply mains in FIG. 7 will now bedescribed.

One example implementation is illustrated in FIG. 8. In FIG. 8, powerline sensor 804 couples to voltage points Hot and Neutral in the powermains 806. FIG. 8 further shows a primary sensor 802 coupled to sensethe differential mode data signal on the twisted pair 808 (e.g. a DSLsignal).

While the example in FIG. 8 exploits the features of a typical wallwart, which has two prongs connecting to Hot and Neutral via a walloutlet, two sensors may be derived if access to Ground is made possible(e.g. by a third prong on a wall wart). This is illustrated in FIG. 9.As shown in FIG. 9, power line sensor 904 includes sensor 906 coupled toHot and Neutral and sensor 908 coupled to Neutral and Ground. Usingvarious wire connections to Hot, Neutral and Ground, the two sensors 906and 908 can be realized in various ways. The noise signal can be sensedbetween Hot and Neutral, or between Neutral and Ground, or between Hotand Ground.

Additionally or alternatively, it is noted that AC signals such as powerline communication signals, such as HP-AV, are transmitteddifferentially between Hot and Neutral on the power mains network andmay convert into CM with respect to ground due to the imbalance of thepower mains network. Accordingly, another possible implementation isshown in FIG. 10. As shown in FIG. 10, before those DM signals coupleinto the CM mode of the twisted pair, a differential and common modecircuit can be devised that connects to the power mains network 1006 inorder to provide two independent outputs from the three wireconnections. A first power line sensor 1002 is connected between the Hotand Neutral wires, while a second power line sensor 1004 is connected atthe mid-point of the first sensor and the ground wire, in order to sensethe CM signal present on the power supply mains, and which is believedto couple into the CM signal of the twisted pair.

In the case of a single point of coupling of external noise from powermains into the DSL cable, it is believed that a single CM sensor at T&Ris sufficient to help cancel multiple noise sources that couple into theDM channel due to the fact that the mode conversion between CM and DM isdetermined by a single transfer function. This single mode conversion isrepresented in FIG. 3, even if there are multiple noise sources on thepower mains. As discussed above in connection with FIG. 5, however, incase of multiple points of coupling, the principle of superpositionwould hold only if the noise source on the power supply is unique or atleast identical at the two points of coupling into the DSL line. In thissituation also, a single CM sensor may be sufficient to mitigate theprojected noise source, even if two coupling paths exist.

However, when there are multiple noise sources and more than onecoupling path, the principle of superposition may no longer hold. Forexample, degeneracy is introduced, so a single CM sensor may not besufficient to mitigate the converted DM noises. The degeneracy may beexpected since the physical distance of the multiple noise sources onthe power mains network with respect to the point of leakage and to thepoint of coupling with the DSL line may differ.

This situation is illustrated in FIG. 11. As shown in FIG. 11, twoseparate noise signals S1 and S2 are transmitted by appliance #1 and #2.As further shown in FIG. 11, the actual composition and leakage of theaggregate noise X and Y at the two points of coupling 1102 (capacitivecoupling between a portion of the twisted pair and the power mains) and1104 (through the power supply coupled to a wall outlet), respectively,may differ. This is due to the fact that, for example, point 1102 iscloser to appliance #1 on the power mains, making noise signal S1 fromappliance #1 more dominant, while point 1104 is closer to appliance #2on the power mains. This difference in dominance is shown in FIG. 11 asdifferent set of weighting coefficients (C1, C2) and (C1′, C2′) in theaggregate noise X and Y, respectively. Because of the different sets ofweighting coefficients, the two noise signals S1 and S2 projectthemselves differently via the two points of coupling 1102 and 1104,respectively, and leakage. In such a case of degeneracy, only a dominantnoise source could be canceled perfectly (either S1 or S2) using asingle CM sensor, if the two noise sources were to overlap in frequency.

Similarly, as shown in FIG. 12, where only one coupling path 1202 isrepresented, power sensor 1204 senses an aggregate noise Y, made of twonoise signals (S1,S2) weighted with weighting coefficients (C1′, C2′) atpoint 1206. This situation is subject to the same degeneracy problem, ifthe aggregate noise X made of the same two noise signals (S1, S2) at thepoint of coupling 1202 is weighted with different weighting coefficients(C1, C2). In this case degeneracy occurs because the projection of thetwo signals S1 and S2 through the coupling point 1202 cannot be made tocoincide simultaneously with the projection of the same two signals S1and S2 sensed through the power sensor 1204.

While a power line sensor may be an alternative to a secondary CMsensor, embodiments of the invention also concurrently use a secondaryCM sensor 1106 and one or more power sensors 1108, as illustrated inFIG. 11. The additional sensor(s) give additional degrees of freedom tolift the degeneracy of the noise projection onto the DSL line, in casethere are multiple noise sources or multiple coupling paths that do notsatisfy to the principle of superposition.

Additionally or alternatively, as shown in FIG. 13, the secondary sensorwith which the power line sensor 1306 can be used concurrently can be adifferential sensor 1302 coupled to an unused pair in the “in-homecable” 1304, since common practice by operators is to use two paircabling within the residence. Cable 1304 could also be another unusedtwisted pair of a drop cable connected to an outside plant drop cablewhich may or may not be connected to the F2 Cables (secondarydistribution cables).

In yet additional or alternative embodiments, as shown in FIG. 14, apower line sensor 1402 according to the invention can be usedconcurrently with a phantom mode (PM) sensor between two differentialDSL pairs 1406 and 1408 whether or not both are being used in a bondingenvironment.

Some considerations for example implementations of a power line sensoraccording to the invention are as follows.

One consideration is that it should provide a differential signal on lowvoltage DC (maybe AC in rare instances) input from an external “wallwart” supply. The DC power supply in a CPE device such as a DSL modem isgenerally designed to filter out unwanted AC noise. A significantattenuation of the noise source is therefore expected. Hence, analternative is to derive a differential signal “directly” (but“isolated”) from AC power mains (i.e. bypassing HF/RF attenuation fromAC:DC conversion stages in an external AC:DC supply).

The power supply sensor signals may not only contain AC noise ofinterest from the mains, but they may also contain noises generated bythe devices on the board. Proper isolation of the sensor to theseunwanted board noises is therefore required.

To estimate and cancel possible noise sources interfering on a “primary”DM channel, one of the following possible sources of “secondary” sensorscan be used: (1) a CM Sensor; (2) a DM sensor on an unused TP; (3) aphantom sensor between two differential mode twisted pairs; or (4) apower line sensor or a set of sensors on the power supply leads (Hot,Neutral, Ground). Alternatively, the secondary sensor can be acombination of one of the individual sensors above, as a linearlyweighted sum of (1) through (4) above.

Alternatively, more than one secondary sensor can be used to estimateand cancel possible noise sources interfering on a “primary” channel.For example, two or more independent secondary sensors can be used witheach sensor attached to only one of (1) through (4) above. Or two ormore independent sensors can be used with each sensor attached tolinearly weighted sums of (1) through (4) above (w/o cross connection).Still further, two or more independent sensors can be used with eachsensor attached to linearly weighted sums of filtered versions of (1)through (4) above (w/o cross connection).

The output signals of the “primary” channel and the output of themultiple “secondary” sensors can be combined in the time domain or inthe frequency domain to estimate and cancel possible noise sourcesinterfering on a “primary” channel. Combination in the time domain canbe done with adaptive linear filtering on the primary and secondarysignals of the multiple sensor inputs. In the frequency domain, the twoor more FFT output vectors (one primary and one or more secondary) canbe linearly combined with a Frequency Domain Equalizer (FEQ)-like set ofweights to produce an improved SNR version of the primary path.

FIG. 18 represents an example embodiment of the invention in which a DMreceiver 1802 is coupled with two secondary sensors, one CM sensor 1804and one Power Line Sensor 1806. Samples from sensors 1804, 1806 areconverted from analog and processed by a time domain digital processingblock 1808, 1810 and then converted to the frequency domain through anFFT operator 1812, 1814. The frequency domain samples of the CM sensor1804 are filtered by a DM-CM Per Tone canceller 1816 and added to the DMsamples in the DM demapper by means of a per Tone Adder 1818, beforebeing equalized by an FEQ and presented to a slicer block. Similarly,the frequency domain samples of the PL sensor are filtered by a DM-PLPer Tone canceller 1820 and added to the DM samples in the DM demapperby means of the per Tone Adder 1818. The per Tone Adder 1818 block takesinput from one or both of the sensors simultaneously. Additionalimplementation aspects of the components in FIG. 18 that can be adaptedfor use in the present invention are described in more detail inco-pending application Ser. No. ______ (12IK05), the contents of whichare incorporated by reference herein in their entirety.

One variation of the frequency domain combination is to maintain two ormore sets of secondary weights corresponding to the DM-CM Per Tonecanceller 1816 and DM-PL Per Tone canceller 1820 and to perform a trialtwo dimensional slicing operation with the slicer (with or withoutTrellis Coded Modulation) using each of the trial weight vectors andcorresponding CM and PL input signals in order to then retain the trialresult with the “best” SNR. This trial can be done on a per tone basisor, with a subset of the bins (e.g. small subset or large subset). Thisvariation provides some improvement of the multi-path degeneracy problem(i.e. two or more aggressors/interferers with different coupling pathsinto the primary sensor and secondary sensor(s) channels).

Another variation is to exploit a time domain “feature” (aka“signature”) to select one of the possible secondary weight sets on aper DMT frame basis to address a situation where multipleaggressors/interferers interfere with the primary channel overlapping infrequency, but not overlapping in time. Another variation is to exploita frequency domain feature/signature to select one of the possible“secondary weight sets” on a per DMT frame basis.

Another purpose of the embodiment presented on FIG. 18 is to enablecharacterization of a noise environment within a house. The sensing ofsignals on the DM port, the CM port and the PL port enablesdetermination of the relative PSD levels of the noise on each sensor, asdescribed above in connection with FIG. 17 a, together withdetermination of a cross correlation level between sensor ports (usingblocks 1822, 1824 and 1826 in FIG. 18). While the PSD levels give anindication of the level of noise on the respective media Twisted Pairand powerline network within a house, the correlation levels betweensensor ports and the associated canceller coefficients translate thelevel of coupling between the propagation modes between the twisted pairmedium and the powerline medium, or on a same medium. For example, ahigh level of correlation between the CM and DM port of the twisted pairis associated with a high level of imbalance of the twisted pair, whichconverts more easily CM signals into DM noise. Similarly, a high levelof correlation between the PL sensor and the CM sensor of the twistedpair is indicative of a strong coupling between the power line and thetwisted pair, which may result from an unusual close proximity of thepowerline network to the twisted pair in the house. Both signal levelsand correlation levels can therefore be used to characterize the noiseenvironment in the house. Also, a comparison of the correlationcoefficients helps determine the possibility of multiple coupling pathsand the level of degeneracy of the coupling of the Power line noise intothe DM sensor. The information derived from the comparison of signallevels and correlation coefficients helps identify the relative locationof disturbers with respect to where sensors sense their respectivesignals, as well as identify the multiplicity of disturbers, wheneverdegeneracy is observed. For example, the relative power of signals, suchas two HPAV transmitters S1 and S2, sensed by a power line sensor suchas that shown in FIG. 11, helps identify which of the two transmittersis closest. The degeneracy observed by comparing the correlationcoefficients computed when either one of them is active helps determinethe number of possible transmitters on the power line networks.

Finally, the concurrent processing of DM, PL and CM sensors enables thedetermination that some DM noises are not coupled from Power Linesources whenever they are visible on the CM and DM sensors and not onthe PL sensor. This situation may arise when coupling of noise takesplace outside of the house, such as the case for RFI coupling into thedrop cable of the twisted pair in CM and DM mode. In this scenario, thesame RFI noise may not be visible on the Power Line sensor.

Finally, the addition of a powerline sensor enables the classificationand identification of home appliances at the source as they may impactthe DSL band of interest. In a house environment, sources ofdisturbances include house appliances, such as vacuum cleaners, lamps,or equipment, such as pool pumps, washing machines, that affect the DSLWAN interface depending on their characteristics, such as whether theyare narrowband or wideband, impulsive or continuous in nature, permanentor intermittent in time. Using a power line sensor, classes ofequipments are derived based on the signals characteristics (bandwidth,amplitude, duration, etc.) of the noise disturbance that they produce onthe power line sensor. In a subsequent step, their impact on the DM DSLport is evaluated by means of the derivation of the correlation metricsand associated canceller coefficients, which represent the degree bywhich powerline noise are projected onto the DM sensor. Access to thosesignal signatures via the power line sensor enable better detection oftheir signatures and of the presence of those noise in the DM DSL port,thereby providing a better tool to identify individually and track thevarious noise sources that make up an aggregate noise environmentaffecting a DSL channel and which originate from the power line network.

FIG. 19 illustrates an example process according to embodiments of theinvention by which signals are detected on the secondary PL sensor andcorrelated to the DM sensor in order to determine the presence of theprojection of PL noise into the DM port. This embodiment can beconsidered a variation of the method and apparatus for effectivelydetecting and characterizing noise and other events affecting acommunications system such as DSL, as detailed in co-pending applicationSer. No. 14/054,552, the contents of which are incorporated herein byreference in their entirety. According to certain aspects, theco-pending application describes a noise analysis engine that isembedded in customer premises equipment that classifies noise sourcesaccording to their specific characteristics and tracks each noise sourcein a dynamic manner, in such a way as to provide visibility to thechanging noise environment within the customer premises and/or reportthis environment to a remote entity. Embodiments of the presentinvention expand the aspects of the co-pending application to operatewith the use of an additional sensor for the purpose of characterizingthe noise environment with better accuracy.

FIG. 19 is a block diagram illustrating an example architecture forimplementing a Noise finder session on the CPE according to embodimentsof the invention. It illustrates the State Machine and processesassociated with the Noise Analysis Engine and in particular how the datacollection thread has been implemented to accommodate the use ofmultiport sensors such as those described in the present invention. Thevarious elements of this architecture are described in more detail asfollows.

Symbol based State Machine 1902. The data collection process operates ona symbol based state machine triggered by the availability of FFT outputdata for two ports, one embodying the DM receiver and a second oneembodying the Power Line sensor or a CM sensor port. A symbol counterwill enable processing of sync symbol and one second event.

Impulse detector 1904: The impulse detection is performed on each symbolbased on time domain or frequency domain information for each sensorport to help determine the presence of an impulse noise source on eachof the two ports.

Quiet Line Noise (QLN) metric 1906: A QLN measurement consists of a pertone average of the power of the noise of each port over the 1 secondwindow to provide primitives to the Line Noise analysis engine. Theaverage is done conditionally on an impulse detector flag or flags.Three PSDs are generated ((a) without impulse—b) with impulse—c) withimpulse only) in order to determine in the analysis engine 1920 thedistinction between impulsive noise of long duration and shortcontinuous noises on any of the two ports.

INM histograms 1908: INM histograms can be populated using the impulsedetector flag as input. If several detector flags are available (e.g.per band, per subband), as many corresponding histograms or alternativetime primitives array are populated over the one second window.

Correlation block 1910: Correlation Signal Processing (SP) is performedin block 1910, between each of the two sensors input, which provides aper tone array such as one presented on FIG. 16 a.

Dual Sensor Canceller (DSC) 1912: a Dual Sensor Canceller block takesthe output of the two sensors in order to predict and cancel thecorrelated noise from the Power Line or Common Mode sensor into the DMreceiver. The output of the DSC block is followed by an impulse detectorblock 1914 and a QLN average block 1916 that uses the processed outputto detect impulses for histogram population in block 1918 and QLNprimitives that are fed to the Noise Monitor Analysis Engine 1920.

An example process for implementing Noise Monitor Analysis Engine 1920according to embodiments of the invention is illustrated in FIG. 20.

As shown, processing for a Noise Monitor Analysis Engine 1920 accordingto embodiments of the present invention extend the principles of theco-pending application by taking input information from additionalsensors, which can be either or both of a CM sensor or a PL sensor. Anobjective of the Noise Monitor Analysis Engine 1920 includesenumerating, after identification and classification, the various typesof noises present on the DSL line. Three or more sets of primitives areinput to this Noise Monitor analysis process; they correspond to theprimitives associated with the impulse histograms 1908 and QLN averages1906 for each of the DM, PL, CM ports as well as the primitivesassociated with the impulse histograms 1918 and QLN averages 1916 foreach of the DM-CM, DM-PL canceller 1914 outputs. Details of theprocessing performed in Threads 0, 1, 2, 3, 4 and 5 shown in FIG. 20 aredescribed in the co-pending application, and those skilled in the artwill be able to understand how to adapt this processing for use with themultiple sensors of the present invention after being taught by thepresent disclosure.

The process of noise detection, classification, signature estimation andlogging depicted on FIG. 20 is done with primitives associated with eachsensor and/or the output of cancellers. The process allows thedetermination of the presence of specific classes of noise on each ofthe sensor as described in the co-pending application. It also allowsdetermining to what degree a noise presence on one of the sensor ispresent on the other sensors, thereby allowing a determination of thecoupling mechanisms between the modes of propagation of the signals onthe mediums (twisted pair, powerline) to which those sensors areconnected.

The process of noise detection, classification, signature estimation andlogging depicted on FIG. 20 is done on primitives that are generatedwhile the modem is not used for data transmission, such as illustratedin FIG. 19. Alternatively, this process can takes place on primitivesgenerated on each of the sensor output, whenever the modem is used forDSL data transmission. These modes correspond respectively to the NoiseFinder and Noise Monitor diagnostic modes described in the co-pendingapplication.

Although the invention has been particularly described herein inconnection with a particularly useful application to DSL communicationsover conventional telephone lines, the invention is not limited to thisapplication. Rather, the principles of the invention can be extended tovarious types of wireline transmission systems such as coaxial cablesystems, including, for example, Multi-Media over COAX (aka MoCA), HPNA(including HPNA 3.1 over COAX), and ITU-T G.hn (including twisted pair,base-band coax and RF coax). For these communication systems, theaddition of a power line sensor help characterize or mitigate theingress of power line noises which find their way onto the coaxial cablemedium, in a similar fashion as they find their way on a twisted pairwithin the home.

Although the present invention has been particularly described withreference to the preferred embodiments thereof, it should be readilyapparent to those of ordinary skill in the art that changes andmodifications in the form and details may be made without departing fromthe spirit and scope of the invention. It is intended that the appendedclaims encompass such changes and modifications.

What is claimed:
 1. An apparatus in a customer premises environment of awireline communication system, comprising: a primary sensor coupled toreceive data signals of the wireline communication system; and a powerline sensor coupled to receive power line signals corresponding to noisesource interferences originating from power mains in the customerpremises environment, wherein the power line sensor is used with theprimary sensor to characterize the noise source interferences to theexclusion of any other secondary sensor.
 2. An apparatus in a customerpremises environment of a wireline communication system, comprising:primary sensor coupled to receive data signals of the wirelinecommunication system; a secondary sensor that is not coupled to receivethe data signals and is coupled to receive a secondary signalcorresponding to noise impacting the data signals, wherein the secondarysensor is one of a common mode sensor and a powerline sensor; and anembedded noise analysis engine that collects information regarding thereceived signals from the sensors and which performs classification ofthe noise based on the information.